Patent GB-589019-A (GB)
Title: Improvements in and relating to jack apparatus
IPC: E02D27/28
Filed: 1939-07-28
Abstract: 589,019. Shoring structures. FREYSSINET, E. July 28, 1939, Nos. 21968 and 21969. Convention dates, Aug. 1, 1938, and June 3, 1939. [Class 20 (ii)] [Also in Groups V, XXIX and XXX] A device for applying pressure which is specially adapted for shoring and strutting, moulding plastic substances and applying tension to metal reinforcements in cast or moulded structures, comprises an enclosure or bag of malleable metal, parts of which are adapted to be deformed when expanded by internal pressure, the bag also including indeformable bearing plates which apply the pressure. The apparatus may be left in, after use, as part of the structure or may be removed, and the expanded apparatus may be filled permanently with cement, synthetic resin, sand or other material. The material in most cases is supplied in liquid form and is kept under pressure until it solidifies. Two bearing plates 1, 2, Fig. 1, are connected by deformable curved plates 3, one of which is connected to a source of liquid pressure at 4. The plates 2 may be embedded in a layer of concrete as shown in order to get a correct bearing of the plates 1, 2 on the structure. In some cases a small quantity of oil is injected into the apparatus with the cement or synthetic resin. This remains fluid and can be withdrawn subsequently to allow a further supply of concrete or resin to be injected to compensate for leakage or shrinkage. In another form of apparatus for forcing two members apart, two of the units are arranged sideby-side and one is filled with synthetic resin and the other with water under pressure. By gradually releasing the water pressure in the one, the other can be made to take an extra supply of resin and is stated to be further expanded in this way in stages between successive inflations of the other apparatus hydraulically. Fig. 10 shows means for tensioning the metal reinforcements of a concrete block or wall. Three superposed sets of apparatus, V<1>, V<2>, V<3> are placed on the lower block 102 before the upper block 112 is cast. The two blocks are then separated to tension the rods 101 before the conduit 104 and the intervening space between the blocks is filled in. Fig. 15 shows a method of tensioning the reinforcement in a concrete ring or annulus. In this case the apparatus 118 is of annular formation and bears radially outwards against the metallic ring 117 carrying the reinforcement 116. One such complete annular jack may be replaced by several segmental jacks. Reference is made also to the provision of the apparatus in the interior of a moulded block so as to apply pressure to it from the interior while it is still plastic. The apparatus can also be introduced into artificial fissures between layers of rock to split off sections instead of using explosives. The Specification as open to inspection under Sect. 91 comprises also the following subjectmatter. Fig. 5 (Cancelled) shows the apparatus in use for shoring and strutting a dam wall 6. The apparatus 9 is inserted under the bracing support 8 and pressure applied between concrete blocks 7a, 8a. Fig 6 (Cancelled) shows two superposed pieces of apparatus 9 fitted in recesses between the head 8a of a buttress and the base 7a where the head 8a is required to be raised. Fig. 20 (Cancelled) shows an apparatus permitting of great expansion but adapted for insertion into a comparatively small bore-hole. It is stated that the various loops 133, 139 in this form are eliminated under expansion and that the apparatus eventually forms a complete cylinder of large diameter. This subject-matter does not appear in the Specification as accepted.